Deficiency of the Deubiquitinase UCHL1 Attenuates Pulmonary Arterial Hypertension.

BACKGROUND: The ubiquitin-proteasome system regulates protein degradation and the development of pulmonary arterial hypertension (PAH), but knowledge about the role of deubiquitinating enzymes in this process is limited. UCHL1 (ubiquitin carboxyl-terminal hydrolase 1), a deubiquitinase, has been shown to reduce AKT1 (AKT serine/threonine kinase 1) degradation, resulting in higher levels. Given that AKT1 is pathological in pulmonary hypertension, we hypothesized that UCHL1 deficiency attenuates PAH development by means of reductions in AKT1. METHODS: Tissues from animal pulmonary hypertension models as well as human pulmonary artery endothelial cells from patients with PAH exhibited increased vascular UCHL1 staining and protein expression. Exposure to LDN57444, a UCHL1-specific inhibitor, reduced human pulmonary artery endothelial cell and smooth muscle cell proliferation. Across 3 preclinical PAH models, LDN57444-exposed animals, Uchl1 knockout rats (Uchl1-/-), and conditional Uchl1 knockout mice (Tie2Cre-Uchl1fl/fl) demonstrated reduced right ventricular hypertrophy, right ventricular systolic pressures, and obliterative vascular remodeling. Lungs and pulmonary artery endothelial cells isolated from Uchl1-/- animals exhibited reduced total and activated Akt with increased ubiquitinated Akt levels. UCHL1-silenced human pulmonary artery endothelial cells displayed reduced lysine(K)63-linked and increased K48-linked AKT1 levels. RESULTS: Supporting experimental data, we found that rs9321, a variant in a GC-enriched region of the UCHL1 gene, is associated with reduced methylation (n=5133), increased UCHL1 gene expression in lungs (n=815), and reduced cardiac index in patients (n=796). In addition, Gadd45α (an established demethylating gene) knockout mice (Gadd45α-/-) exhibited reduced lung vascular UCHL1 and AKT1 expression along with attenuated hypoxic pulmonary hypertension. CONCLUSIONS: Our findings suggest that UCHL1 deficiency results in PAH attenuation by means of reduced AKT1, highlighting a novel therapeutic pathway in PAH.

Hypusine Signaling Promotes Pulmonary Vascular Remodeling in Pulmonary Arterial Hypertension.

RATIONALE: The ubiquitous polyamine spermidine is essential for cell survival and proliferation. One important function of spermidine is to serve as a substrate for hypusination, a post-translational modification process that occurs exclusively on eukaryotic translation factor 5A (eIF5A) and ensures efficient translation of various gene products. Pulmonary arterial hypertension (PAH) is a life-threatening disease characterized by progressive obliteration of the small pulmonary arteries (PAs) due to excessive proliferation of PA smooth muscle cells (PASMCs) and suppressed apoptosis. OBJECTIVES: To characterize the role of hypusine signaling in PAH. METHODS: Molecular, genetic, and pharmacological approaches were used both in vitro and in vivo to investigate the role of hypusine signaling in pulmonary vascular remodeling. MEASUREMENTS AND MAIN RESULTS: Hypusine forming enzymes (deoxyhypusine synthase, DHPS and deoxyhypusine hydroxylase, DOHH) and hypusinated eIF5A are overexpressed in distal PAs and isolated PASMCs from PAH patients and animal models. In vitro, inhibition of DHPS using GC7 or short hairpin RNA resulted in a decrease in PAH-PASMC resistance to apoptosis and proliferation. In vivo, inactivation of one allele of Dhps targeted to smooth muscle cells alleviates PAH in mice and that its pharmacological inhibition significantly decreases pulmonary vascular remodeling and improves hemodynamics and cardiac function in two rat models of established PAH. Using mass spectrometry, we show that hypusine signaling promotes the expression of a broad array of proteins involved in oxidative phosphorylation, thus supporting the bioenergetic requirements of cell survival and proliferation. CONCLUSIONS: These findings support inhibiting hypusine signaling as a potential treatment for PAH.

G9a/GLP Targeting Ameliorates Pulmonary Vascular Remodeling in Pulmonary Arterial Hypertension.

Pulmonary arterial hypertension (PAH) is characterized by progressive vascular remodeling of small pulmonary arteries (PAs) causing sustained elevation of PA pressure, right ventricular failure, and death. Similar to cancer cells, PA smooth muscle cells (PASMCs), which play a key role in pulmonary vascular remodeling, have adopted multiple mechanisms to sustain their survival and proliferation in the presence of stress. The histone methyltransferase G9a and its partner protein GLP (G9a-like protein) have been shown to exert oncogenic effects and to serve as a buffer against an exaggerated transcriptional response. Therefore, we hypothesized that upregulation of G9a and GLP in PAH plays a pivotal role in pulmonary vascular remodeling by maintaining the abnormal phenotype of PAH-PASMCs. We found that G9a is increased in PASMCs from patients with PAH as well as in remodeled PAs from animal models. Pharmacological inhibition of G9a/GLP activity using BIX01294 and UNC0642 significantly reduced the prosurvival and proproliferative potentials of cultured PAH-PASMCs. Using RNA sequencing, further exploration revealed that G9a/GLP promotes extracellular matrix production and affords protection against the negative effects of an overactive stress response. Finally, we found that therapeutic treatment with BIX01294 reduced pulmonary vascular remodeling and lowered mean PA pressure in fawn-hooded rats. Treatment of Sugen/hypoxia-challenged mice with BIX01294 also improved pulmonary hemodynamics and right ventricular function. In conclusion, these findings indicate that G9a/GLP inhibition may represent a new therapeutic approach in PAH.

Right Ventricular Maladaptation to Pressure Overload in Fischer Rats Is Associated With Profound Deficiency in Adenylate Kinase 1 and Impaired Ventricular Energetics.

BACKGROUND: We explored the mechanism of maladaptive right ventricular (RV) remodeling in Fischer compared with Sprague-Dawley (SD) rats exposed to pressure overload. METHODS: Pulmonary hypertension was induced by injection of the VEGFR antagonist, SU5416, followed by a 3-week exposure to hypoxia (Sugen chronic hypoxia). In vivo oxidative metabolism was assessed by RV/left ventricle ratio of [11C]acetate positron emission tomography clearance (kmono). Unbiased, global transcriptional and proteomic profiling was performed in Fischer and SD rats at baseline and after Sugen chronic hypoxia. RESULTS: All Fischer rats succumbed to RV failure by 5 weeks, whereas SD rats showed preserved RV function and 88% survival beyond 9 weeks (P<0.0001). Fischer rats exhibited increased oxidative metabolism at 4 weeks (P<0.05) and impaired RV efficiency compared with SD (work metabolic index: 52±10 versus 91±27 mmHg·mL/cm2, respectively; P<0.05), but no differences in mitochondrial complex activity. AK1 (adenylate kinase 1) was among the top 10 differentially expressed genes between Fischer and SD rats, with markedly lower RV expression in Fischer rats (FC: 3.36, P<0.05), confirmed by proteomic analysis and validated by Western blotting (>10-fold reduction, P<0.001). While whole-genome sequencing failed to reveal any coding region mutations in Fischer rats, there was a unique variant in a highly conserved upstream flanking region likely involved in the regulation of AK1 expression. CONCLUSIONS: Therefore, Fischer rats exhibit profound AK1 deficiency and inefficient cardiac energetics likely related to reduced adenosine triphosphate shuttling from the mitochondria to the contractile fibers. This represents a novel mechanism for RV failure in response to chronic increases in afterload.

Neutrophil-Lymphocyte Ratio as an Independent Predictor of Survival in Pulmonary Arterial Hypertension: An Exploratory Study.

Background: The blood neutrophil-to-lymphocyte ratio (NLR) has recently emerged as a powerful predictor of adverse outcomes in some cardiovascular and lung diseases. Pulmonary arterial hypertension (PAH) is a lethal vasculopathy associated with increased inflammation. Although PAH exhibits a higher prevalence among women, men have a poorer prognosis. We investigated the NLR as an independent predictor of transplant-free survival in PAH. Methods: We performed a retrospective analysis of 78 PAH patients from the Quebec PAHBiobank (71% female). We used univariate and multivariate (adjusted for age, sex, renal function, and disease severity) Cox regression analyses to assess the relationship between the NLR and transplant-free survival, in the whole sample, and according to sex. The NLR was categorized as high (≥ 4.8) or low (< 4.8) using receiver operating characteristic analysis. Unadjusted Kaplan-Meier analysis estimated survival per NLR category. Results: The NLR was higher in patients who died, compared to that in patients who had transplant-free survival (P < 0.05). The NLR was an independent predictor of event-free survival in PAH (unadjusted hazard ratio: 1.11, 95% confidence interval: 1.04-1.18, which remained significant after adjustment for covariates). The high-NLR group had lower 1-, 3-, and 5-year survival compared to those with a low NLR (P < 0.001). The NLR remains a predictor of survival in women. Conclusions: The NLR is an independent predictor of transplant-free survival in PAH. We report a potential sexual dimorphism in the ability of the NLR to predict mortality in PAH, emphasizing the importance of considering sex-related differences in the development of biomarkers in PAH.

Contexte: Le rapport neutrophiles/lymphocytes (RNL) s'est récemment imposé comme un puissant facteur prédictif de l'issue défavorable de certaines maladies cardiovasculaires et pulmonaires. L'hypertension artérielle pulmonaire (HTAP) est une vasculopathie mortelle associée à une inflammation accrue. Bien que sa prévalence soit plus élevée chez les femmes, son pronostic est plus défavorable chez les hommes. Nous avons étudié le RNL en tant que prédicteur indépendant de la survie sans greffe chez des sujets atteints d'HTAP. Méthodologie: Nous avons effectué une analyse rétrospective du matériel sur l'HTAP de la Biobanque du Québec se rapportant à 78 patients (71 % de femmes). Des analyses de régression de Cox univariées et multivariées (ajustées en fonction de l'âge, du sexe, de la fonction rénale et de la gravité de la maladie) nous ont permis d'évaluer la relation entre le RNL et la survie sans greffe dans l'ensemble de l'échantillon et selon le sexe. Le RNL a été classé comme élevé (≥ 4,8) ou faible (< 4,8) au terme d'une analyse des caractéristiques de fonctionnement du récepteur. Une analyse non ajustée effectuée selon la méthode de Kaplan-Meier a servi à estimer la survie par catégorie de RNL. Résultats: Le RNL était plus élevé chez les patients décédés que chez les patients ayant survécu sans greffe (p < 0,05). Le RNL était un prédicteur indépendant de la survie sans événement chez les patients atteints d'HTAP (rapport des risques instantanés non ajusté : 1,11, intervalle de confiance à 95 % : 1,04-1,18, demeuré significatif après ajustement en fonction des covariables). La survie à 1, 3 et 5 ans a été inférieure au sein du groupe présentant un RNL élevé comparativement au groupe présentant un RNL faible (p < 0,001). Le RNL demeure un prédicteur de la survie chez les femmes. Conclusions: Le RNL est un facteur prédictif indépendant de la survie sans greffe chez les sujets atteints d'HTAP. Selon nos observations, un dimorphisme sexuel potentiel le caractérise en tant que prédicteur de la mortalité chez les sujets atteints d'HTAP. Il importe donc de tenir compte des différences liées au sexe dans le développement des biomarqueurs de l'HTAP.

PARP1-PKM2 Axis Mediates Right Ventricular Failure Associated With Pulmonary Arterial Hypertension.

The authors show that increased poly(adenosine diphosphate-ribose) polymerase 1 (PARP1) and pyruvate kinase muscle isozyme 2 (PKM2) expression is a common feature of a decompensated right ventricle in patients with pulmonary arterial hypertension and animal models. The authors find in vitro that overactivated PARP1 promotes cardiomyocyte dysfunction by favoring PKM2 expression and nuclear function, glycolytic gene expression, activation of nuclear factor κB-dependent proinflammatory factors. Pharmacologic and genetic inhibition of PARP1 or enforced tetramerization of PKM2 attenuates maladaptive remodeling improving right ventricular (RV) function in multiple rodent models. Taken together, these data implicate the PARP1/PKM2 axis as a critical driver of maladaptive RV remodeling and a new promising target to directly sustain RV function in patients with pulmonary arterial hypertension.

Noncanonical HIPPO/MST Signaling via BUB3 and FOXO Drives Pulmonary Vascular Cell Growth and Survival.

RATIONALE: The MSTs (mammalian Ste20-like kinases) 1/2 are members of the HIPPO pathway that act as growth suppressors in adult proliferative diseases. Pulmonary arterial hypertension (PAH) manifests by increased proliferation and survival of pulmonary vascular cells in small PAs, pulmonary vascular remodeling, and the rise of pulmonary arterial pressure. The role of MST1/2 in PAH is currently unknown. OBJECTIVE: To investigate the roles and mechanisms of the action of MST1 and MST2 in PAH. METHODS AND RESULTS: Using early-passage pulmonary vascular cells from PAH and nondiseased lungs and mice with smooth muscle-specific tamoxifen-inducible Mst1/2 knockdown, we found that, in contrast to canonical antiproliferative/proapoptotic roles, MST1/2 act as proproliferative/prosurvival molecules in human PAH pulmonary arterial vascular smooth muscle cells and pulmonary arterial adventitial fibroblasts and support established pulmonary vascular remodeling and pulmonary hypertension in mice with SU5416/hypoxia-induced pulmonary hypertension. By using unbiased proteomic analysis, gain- and loss-of function approaches, and pharmacological inhibition of MST1/2 kinase activity by XMU-MP-1, we next evaluated mechanisms of regulation and function of MST1/2 in PAH pulmonary vascular cells. We found that, in PAH pulmonary arterial adventitial fibroblasts, the proproliferative function of MST1/2 is caused by IL-6-dependent MST1/2 overexpression, which induces PSMC6-dependent downregulation of forkhead homeobox type O 3 and hyperproliferation. In PAH pulmonary arterial vascular smooth muscle cells, MST1/2 acted via forming a disease-specific interaction with BUB3 and supported ECM (extracellular matrix)- and USP10-dependent BUB3 accumulation, upregulation of Akt-mTORC1, cell proliferation, and survival. Supporting our in vitro observations, smooth muscle-specific Mst1/2 knockdown halted upregulation of Akt-mTORC1 in small muscular PAs of mice with SU5416/hypoxia-induced pulmonary hypertension. CONCLUSIONS: Together, this study describes a novel proproliferative/prosurvival role of MST1/2 in PAH pulmonary vasculature, provides a novel mechanistic link from MST1/2 via BUB3 and forkhead homeobox type O to the abnormal proliferation and survival of pulmonary arterial vascular smooth muscle cells and pulmonary arterial adventitial fibroblasts, remodeling and pulmonary hypertension, and suggests new target pathways for therapeutic intervention.

Potential for inhibition of checkpoint kinases 1/2 in pulmonary fibrosis and secondary pulmonary hypertension.

BACKGROUND: Idiopathic pulmonary fibrosis (IPF) is a chronic lung disease characterised by exuberant tissue remodelling and associated with high unmet medical needs. Outcomes are even worse when IPF results in secondary pulmonary hypertension (PH). Importantly, exaggerated resistance to cell death, excessive proliferation and enhanced synthetic capacity are key endophenotypes of both fibroblasts and pulmonary artery smooth muscle cells, suggesting shared molecular pathways. Under persistent injury, sustained activation of the DNA damage response (DDR) is integral to the preservation of cells survival and their capacity to proliferate. Checkpoint kinases 1 and 2 (CHK1/2) are key components of the DDR. The objective of this study was to assess the role of CHK1/2 in the development and progression of IPF and IPF+PH. METHODS AND RESULTS: Increased expression of DNA damage markers and CHK1/2 were observed in lungs, remodelled pulmonary arteries and isolated fibroblasts from IPF patients and animal models. Blockade of CHK1/2 expression or activity-induced DNA damage overload and reverted the apoptosis-resistant and fibroproliferative phenotype of disease cells. Moreover, inhibition of CHK1/2 was sufficient to interfere with transforming growth factor beta 1-mediated fibroblast activation. Importantly, pharmacological inhibition of CHK1/2 using LY2606368 attenuated fibrosis and pulmonary vascular remodelling leading to improvement in respiratory mechanics and haemodynamic parameters in two animal models mimicking IPF and IPF+PH. CONCLUSION: This study identifies CHK1/2 as key regulators of lung fibrosis and provides a proof of principle for CHK1/2 inhibition as a potential novel therapeutic option for IPF and IPF+PH.

Implication of EZH2 in the Pro-Proliferative and Apoptosis-Resistant Phenotype of Pulmonary Artery Smooth Muscle Cells in PAH: A Transcriptomic and Proteomic Approach.

Pulmonary arterial hypertension (PAH) is a progressive disorder characterized by a sustained elevation of pulmonary artery (PA) pressure, right ventricular failure, and premature death. Enhanced proliferation and resistance to apoptosis (as seen in cancer cells) of PA smooth muscle cells (PASMCs) is a major pathological hallmark contributing to pulmonary vascular remodeling in PAH, for which current therapies have only limited effects. Emerging evidence points toward a critical role for Enhancer of Zeste Homolog 2 (EZH2) in cancer cell proliferation and survival. However, its role in PAH remains largely unknown. The aim of this study was to determine whether EZH2 represents a new factor critically involved in the abnormal phenotype of PAH-PASMCs. We found that EZH2 is overexpressed in human lung tissues and isolated PASMCs from PAH patients compared to controls as well as in two animal models mimicking the disease. Through loss- and gain-of-function approaches, we showed that EZH2 promotes PAH-PASMC proliferation and survival. By combining quantitative transcriptomic and proteomic approaches in PAH-PASMCs subjected or not to EZH2 knockdown, we found that inhibition of EZH2 downregulates many factors involved in cell-cycle progression, including E2F targets, and contributes to maintain energy production. Notably, we found that EZH2 promotes expression of several nuclear-encoded components of the mitochondrial translation machinery and tricarboxylic acid cycle genes. Overall, this study provides evidence that, by overexpressing EZH2, PAH-PASMCs remove the physiological breaks that normally restrain their proliferation and susceptibility to apoptosis and suggests that EZH2 or downstream factors may serve as therapeutic targets to combat pulmonary vascular remodeling.

Preclinical Investigation of Trifluoperazine as a Novel Therapeutic Agent for the Treatment of Pulmonary Arterial Hypertension.

Trifluoperazine (TFP), an antipsychotic drug approved by the Food and Drug Administration, has been show to exhibit anti-cancer effects. Pulmonary arterial hypertension (PAH) is a devastating disease characterized by a progressive obliteration of small pulmonary arteries (PAs) due to exaggerated proliferation and resistance to apoptosis of PA smooth muscle cells (PASMCs). However, the therapeutic potential of TFP for correcting the cancer-like phenotype of PAH-PASMCs and improving PAH in animal models remains unknown. PASMCs isolated from PAH patients were exposed to different concentrations of TFP before assessments of cell proliferation and apoptosis. The in vivo therapeutic potential of TFP was tested in two preclinical models with established PAH, namely the monocrotaline and sugen/hypoxia-induced rat models. Assessments of hemodynamics by right heart catheterization and histopathology were conducted. TFP showed strong anti-survival and anti-proliferative effects on cultured PAH-PASMCs. Exposure to TFP was associated with downregulation of AKT activity and nuclear translocation of forkhead box protein O3 (FOXO3). In both preclinical models, TFP significantly lowered the right ventricular systolic pressure and total pulmonary resistance and improved cardiac function. Consistently, TFP reduced the medial wall thickness of distal PAs. Overall, our data indicate that TFP could have beneficial effects in PAH and support the view that seeking new uses for old drugs may represent a fruitful approach.

17ß-Estradiol and estrogen receptor α protect right ventricular function in pulmonary hypertension via BMPR2 and apelin.

Women with pulmonary arterial hypertension (PAH) exhibit better right ventricular (RV) function and survival than men; however, the underlying mechanisms are unknown. We hypothesized that 17ß-estradiol (E2), through estrogen receptor α (ER-α), attenuates PAH-induced RV failure (RVF) by upregulating the procontractile and prosurvival peptide apelin via a BMPR2-dependent mechanism. We found that ER-α and apelin expression were decreased in RV homogenates from patients with RVF and from rats with maladaptive (but not adaptive) RV remodeling. RV cardiomyocyte apelin abundance increased in vivo or in vitro after treatment with E2 or ER-α agonist. Studies employing ER-α-null or ER-ß-null mice, ER-α loss-of-function mutant rats, or siRNA demonstrated that ER-α is necessary for E2 to upregulate RV apelin. E2 and ER-α increased BMPR2 in pulmonary hypertension RVs and in isolated RV cardiomyocytes, associated with ER-α binding to the Bmpr2 promoter. BMPR2 is required for E2-mediated increases in apelin abundance, and both BMPR2 and apelin are necessary for E2 to exert RV-protective effects. E2 or ER-α agonist rescued monocrotaline pulmonary hypertension and restored RV apelin and BMPR2. We identified what we believe to be a novel cardioprotective E2/ER-α/BMPR2/apelin axis in the RV. Harnessing this axis may lead to novel RV-targeted therapies for PAH patients of either sex.

Oxidized DNA Precursors Cleanup by NUDT1 Contributes to Vascular Remodeling in Pulmonary Arterial Hypertension.

Rationale: Pulmonary arterial hypertension (PAH) is a life-threatening condition characterized by abnormally elevated pulmonary pressures and right ventricular failure. Excessive proliferation and resistance to apoptosis of pulmonary artery smooth muscle cells (PASMCs) is one of the most important drivers of vascular remodeling in PAH, for which available treatments have limited effectiveness.Objectives: To gain insights into the mechanisms leading to the development of the disease and identify new actionable targets.Methods: Protein expression profiling was conducted by two-dimensional liquid chromatography coupled to tandem mass spectrometry in isolated PASMCs from controls and patients with PAH. Multiple molecular, biochemical, and pharmacologic approaches were used to decipher the role of NUDT1 (nudrix hyrolase 1) in PAH.Measurements and Main Results: Increased expression of the detoxifying DNA enzyme NUDT1 was detected in cells and tissues from patients with PAH and animal models. In vitro, molecular or pharmacological inhibition of NUDT1 in PAH-PASMCs induced accumulation of oxidized nucleotides in the DNA, irresolvable DNA damage (comet assay), disruption of cellular bioenergetics (Seahorse), and cell death (terminal deoxynucleotidyl transferase dUTP nick end labeling assay). In two animal models with established PAH (i.e., monocrotaline and Sugen/hypoxia-treated rats), pharmacological inhibition of NUDT1 using (S)-Crizotinib significantly decreased pulmonary vascular remodeling and improved hemodynamics and cardiac function.Conclusions: Our results indicate that, by overexpressing NUDT1, PAH-PASMCs hijack persistent oxidative stress in preventing incorporation of oxidized nucleotides into DNA, thus allowing the cell to escape apoptosis and proliferate. Given that NUDT1 inhibitors are under clinical investigation for cancer, they may represent a new therapeutic option for PAH.

Identification of Long Noncoding RNA H19 as a New Biomarker and Therapeutic Target in Right Ventricular Failure in Pulmonary Arterial Hypertension.

BACKGROUND: Right ventricular (RV) function is the major determinant for both functional capacity and survival in patients with pulmonary arterial hypertension (PAH). Despite the recognized clinical importance of preserving RV function, the subcellular mechanisms that govern the transition from a compensated to a decompensated state remain poorly understood and as a consequence there are no clinically established treatments for RV failure and a paucity of clinically useful biomarkers. Accumulating evidence indicates that long noncoding RNAs are powerful regulators of cardiac development and disease. Nonetheless, their implication in adverse RV remodeling in PAH is unknown. METHODS: Expression of the long noncoding RNA H19 was assessed by quantitative PCR in plasma and RV from patients categorized as control RV, compensated RV or decompensated RV based on clinical history and cardiac index. The impact of H19 suppression using GapmeR was explored in 2 rat models mimicking RV failure, namely the monocrotaline and pulmonary artery banding. Echocardiographic, hemodynamic, histological, and biochemical analyses were conducted. In vitro gain- and loss-of-function experiments were performed in rat cardiomyocytes. RESULTS: We demonstrated that H19 is upregulated in decompensated RV from PAH patients and correlates with RV hypertrophy and fibrosis. Similar findings were observed in monocrotaline and pulmonary artery banding rats. We found that silencing H19 limits pathological RV hypertrophy, fibrosis and capillary rarefaction, thus preserving RV function in monocrotaline and pulmonary artery banding rats without affecting pulmonary vascular remodeling. This cardioprotective effect was accompanied by E2F transcription factor 1-mediated upregulation of enhancer of zeste homolog 2. In vitro, knockdown of H19 suppressed cardiomyocyte hypertrophy induced by phenylephrine, while its overexpression has the opposite effect. Finally, we demonstrated that circulating H19 levels in plasma discriminate PAH patients from controls, correlate with RV function and predict long-term survival in 2 independent idiopathic PAH cohorts. Moreover, H19 levels delineate subgroups of patients with differentiated prognosis when combined with the NT-proBNP (N-terminal pro-B-type natriuretic peptide) levels or the risk score proposed by both REVEAL (Registry to Evaluate Early and Long-Term PAH Disease Management) and the 2015 European Pulmonary Hypertension Guidelines. CONCLUSIONS: Our findings identify H19 as a new therapeutic target to impede the development of maladaptive RV remodeling and a promising biomarker of PAH severity and prognosis.

Effect of p53 activation on experimental right ventricular hypertrophy.

The leading cause of death in Pulmonary Arterial Hypertension (PAH) is right ventricular (RV) failure. The tumor suppressor p53 has been associated with left ventricular hypertrophy (LVH) and remodeling but its role in RV hypertrophy (RVH) is unclear. The purpose of this study was to determine whether pharmacological activation of p53 by Quinacrine affects RV remodeling and function in the pulmonary artery banding (PAB) model of compensated RVH in mice. The effects of p53 activation on cellular functions were studied in isolated cardiomyocytes, cardiac fibroblasts and endothelial cells (ECs). The expression of p53 was examined both on human RV tissues from patients with compensated and decompensated RVH and in mouse RV tissues early and late after the PAB. As compared to control human RVs, there was no change in p53 expression in compensated RVH, while a marked upregulation was found in decompensated RVH. Similarly, in comparison to SHAM-operated mice, unaltered RV p53 expression 7 days after PAB, was markedly induced 21 days after the PAB. Quinacrine induced p53 accumulation did not further deteriorate RV function at day 7 after PAB. Quinacrine administration did not increase EC death, neither diminished EC number and capillary density in RV tissues. No major impact on the expression of markers of sarcomere organization, fatty acid and mitochondrial metabolism and respiration was noted in Quinacrine-treated PAB mice. p53 accumulation modulated the expression of Heme Oxygenase 1 (HO-1) and Glucose Transporter (Glut1) in mouse RVs and in adult cardiomyocytes. We conclude that early p53 activation in PAB-induced RVH does not cause substantial detrimental effects on right ventricular remodeling and function.

Metabolic Syndrome Exacerbates Pulmonary Hypertension due to Left Heart Disease.

RATIONALE: Pulmonary hypertension (PH) due to left heart disease (LHD), or group 2 PH, is the most prevalent form of PH worldwide. PH due to LHD is often associated with metabolic syndrome (MetS). In 12% to 13% of cases, patients with PH due to LHD display vascular remodeling of pulmonary arteries (PAs) associated with poor prognosis. Unfortunately, the underlying mechanisms remain unknown; PH-targeted therapies for this group are nonexistent, and the development of a new preclinical model is crucial. Among the numerous pathways dysregulated in MetS, inflammation plays also a critical role in both PH and vascular remodeling. OBJECTIVE: We hypothesized that MetS and inflammation may trigger the development of vascular remodeling in group 2 PH. METHODS AND RESULTS: Using supracoronary aortic banding, we induced diastolic dysfunction in rats. Then we induced MetS by a combination of high-fat diet and olanzapine treatment. We used metformin treatment and anti-IL-6 (interleukin-6) antibodies to inhibit the IL-6 pathway. Compared with sham conditions, only supracoronary aortic banding+MetS rats developed precapillary PH, as measured by both echocardiography and right/left heart catheterization. PH in supracoronary aortic banding+MetS was associated with macrophage accumulation and increased IL-6 production in lung. PH was also associated with STAT3 (signal transducer and activator of transcription 3) activation and increased proliferation of PA smooth muscle cells, which contributes to remodeling of distal PA. We reported macrophage accumulation, increased IL-6 levels, and STAT3 activation in the lung of group 2 PH patients. In vitro, IL-6 activates STAT3 and induces human PA smooth muscle cell proliferation. Metformin treatment decreased inflammation, IL-6 levels, STAT3 activation, and human PA smooth muscle cell proliferation. In vivo, in the supracoronary aortic banding+MetS animals, reducing IL-6, either by anti-IL-6 antibody or metformin treatment, reversed pulmonary vascular remodeling and improve PH due to LHD. CONCLUSIONS: We developed a new preclinical model of group 2 PH by combining MetS with LHD. We showed that MetS exacerbates group 2 PH. We provided evidence for the importance of the IL-6-STAT3 pathway in our experimental model of group 2 PH and human patients.

Inhibition of CHK 1 (Checkpoint Kinase 1) Elicits Therapeutic Effects in Pulmonary Arterial Hypertension.

OBJECTIVE: Pulmonary arterial hypertension (PAH) is a debilitating disease associated with progressive vascular remodeling of distal pulmonary arteries leading to elevation of pulmonary artery pressure, right ventricular hypertrophy, and death. Although presenting high levels of DNA damage that normally jeopardize their viability, pulmonary artery smooth muscle cells (PASMCs) from patients with PAH exhibit a cancer-like proproliferative and apoptosis-resistant phenotype accounting for vascular lumen obliteration. In cancer cells, overexpression of the serine/threonine-protein kinase CHK1 (checkpoint kinase 1) is exploited to counteract the excess of DNA damage insults they are exposed to. This study aimed to determine whether PAH-PASMCs have developed an orchestrated response mediated by CHK1 to overcome DNA damage, allowing cell survival and proliferation. Approach and Results: We demonstrated that CHK1 expression is markedly increased in isolated PASMCs and distal PAs from patients with PAH compared with controls, as well as in multiple complementary animal models recapitulating the disease, including monocrotaline rats and the simian immunodeficiency virus-infected macaques. Using a pharmacological and molecular loss of function approach, we showed that CHK1 promotes PAH-PASMCs proliferation and resistance to apoptosis. In addition, we found that inhibition of CHK1 induces downregulation of the DNA repair protein RAD 51 and severe DNA damage. In vivo, we provided evidence that pharmacological inhibition of CHK1 significantly reduces vascular remodeling and improves hemodynamic parameters in 2 experimental rat models of PAH. CONCLUSIONS: Our results show that CHK1 exerts a proproliferative function in PAH-PASMCs by mitigating DNA damage and suggest that CHK1 inhibition may, therefore, represent an attractive therapeutic option for patients with PAH.